* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-size: 16px;
  font-family: 'Roboto', sans-serif;
  color: white;
  background-color: #151515;
}

h1 {
  font-size: 25px;
  font-weight: 500;
}

.container {
  width: 1200px;      
  padding: 0 15px;
  display: flex;
  justify-content: space-between;
}

/* header > nav.container > ul > li:last-child {
  float: right;
} */

header > nav {
  height: 60px;
  line-height: 60px;
  background-color: #151515;
  border-bottom: 1px solid #515151;
  font-weight: 400;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  margin-left: 8px;
}

header > nav > ul {
  padding: 0;
  margin: 0;
}

header > nav > ul > li {
  display: inline;
  margin-right: 15px;
}

header > nav > ul > li:last-child {
  float: right;
}

header > nav > ul > li:last-child > a {
  /* border: 1px solid #fff; */
  padding: 8px 12px;
  text-decoration: none;
  color: #fff;
  transition: all 0.3s ease;
}

#index a {
  border: 1px solid white;
}

#index a:hover {
  background-color: #fff;
  color: #151515;
}

header > nav > ul > li:last-child > a:hover {
  /* background-color: #fff; */ 
  color: #fff;
}

header > nav > ul > li > a:link,
header > nav > ul > li > a:visited {
  color: white;
  text-decoration: none;
}

header > nav > ul > li > a:hover,
header > nav > ul > li > a:active {
  text-decoration: underline;
}
    
.main-section {
  max-width: 1200px;
  padding-top: 60px;
}

section.introduction > p{
  font-size: 40px;
  line-height: 1.2;
  margin-bottom: 30px;
  margin-top: 15px;
}

section.introduction > h1{
  font-size: 60px;
  margin-bottom: 5px;
}

section.introduction {
  border-bottom: 1px solid #515151;
  font-weight: 500;
  padding: 0 20px;
}
  
article.colSx {
  width: 60%;
  line-height: 1.4;
  float: left;
  padding: 0 15px;
  border-right: 1px solid #515151;
  font-weight: 200;
}

article.colSx > section{
  padding-bottom: 30px;
}

aside.image-container {
  width: 40%;
  line-height: 1.4;
  float: right;
  padding: 0 15px;
  font-size: 14px;
  font-weight: 400;
}

aside a {
  color: white;
  text-decoration: underline;
}

.img_01{
  margin-top: 80px;
}

.img_02{
  margin-top: 50px;
}

.img_03{
  margin-top: 50px;
}

.img_04{
  margin-top: 50px;
}

.img_05 {
margin-top: 50px;
}

.img_06 {
  margin-top: 50px;
  }

.image-container a:visited 
.image-container a:link {
  color: white;
  text-decoration: underline;
}

footer {
  height: 70px;
  width: 100%;
  border-top: 1px solid #515151;
  font-weight: 400;
  line-height: 1.5;
}

footer a[href] {
  color: #555;
}

footer p:nth-of-type(1){
  width: 60%;
  float: left;
}

footer p:nth-of-type(2) {
  width: 40%;
  float: right;
  font-size: 14px;
  color: #555;
}

@media only screen and (max-width: 600px) {

  .container,
  main > article.colSx,
  main > aside.image-container {
      width: 100%;
      flex-wrap: wrap;
  }

  article.colSx {
    border-right: none;
  }

  section.introduction > img{
    width: 100%;
  }

  section.introduction > h1{
    font-size: 55px;
  }

  section.introduction > p{
    font-size: 35px;
    line-height: 1.2;
  }

  .image-container {
    width: 100%;
    justify-content: center;
    align-items: center;
    margin: 0 auto;
  }

  .img_03{
    margin-top: 50px;
  }

  .img_04{
    margin-bottom: 50px;
  }

  footer p:nth-of-type(2) {
    width: 100%;
  }

  footer,
  footer p:nth-of-type(2),
  footer p:nth-of-type(1) {
    width: 100%;
    flex-wrap: wrap;
  }

}